Process and composition for the preparation of reflecting surfaces



Patented Mar. 30, 1943 2,315,141.

Pnooass AND COMPOSITION FOR rm: PREPARATION OF amac'rmo SURFACES Philip F. Tryon, Terre- Haute, Ind., asslgnor to ing structural formula:

Commercial Solvents Corporation, Terre Haute, Ind., a corporation of Maryland No Drawing. Application April 19, 1942. Serial No. 438,307

8 Claims. (01. 117935) The present invention relates to a novel prooess for obtaining mirrored surfaces and to suitable compositions for producing the same. "More particularly, it relates to the use of nitro alcohols as active ingredients in mirror-forming compositions, said nitro alcohols having the follow- NO: H the object upon which the reflecting surface is to be produced. In this connection, the expresslon silver ammonia complexf which appears in which the substituents R and R may rep- 'resent either hydroxyalkyl, hydrogen, or an alkyl group, and It represents either hydrogen, aryl,

the utilization of which results in the Droduetion of highly satisfactory reflecting surfaces,

without encountering the disadvantages cha'racteristic of the methods formerly employed. In carrying out my invention, bright silver mirrors may be obtained by adding a solutionof a suitable base to a solution containing a nitro alcohol,.'of the, type mentioned above, and a silver ammonia complex. The basic solution is preferably. added with agitation attemperatures of from about -80 C., to the solution containing the nitro alcohol and the silver ammonia complex, the latter solution being in contact with in the disclosure as well as in certain of the appended claims, is to be interpreted to include.

in addition to the complex formed from amalkyl. l5 monia. and a silversalt, the complexes resulting The production of mirrors, such as those of from" silver salts and an alkyl-substituted amthe silver type, has in the past been. achieved monia, such as for example 2-aminobutane, triby the use of a composition containing a 'commethylamine. diethylamine, N-(Z-aminoisopound of silver in a readily-reducible form. 511- .butyhisopropylamine, v and the like.

vering compositions typical of those previously 20 Although in general the best results are obemployed were prepared by dissolving a suitable tained' by employing. approximately equivalent silver salt such as silver nitrate in water, and quantities of reactants at temperatures of from adding thereto a solution of potassium or sodium 20-80 C.. it willbe found that these conditions hydroxide until precipitation of silver oxide apmay be varied within relativel wide limits. The peared to be complete. To this mixture was then principal factors ordinarily resp or I introduced aqueous ammonia until all. ofthe st ss tating changes i pr por i n of e ct silver oxide had completely diss01ved and the and reaction conditions are the natureof the object to be coated with silver then placed in surface to be coated. the desired rate of depos this solution, after which a material containing tion of s lver. and the desired degree of brighta reactive aldehyde group such as glucose, was ne' s of the mirrorto be produced. v r added. Although within certain relatively nar- Anv of the silver salts that are capable of row limits such composition are capable of givf min a complex with ammonia or the aboveing satisfactory reflecting surfaces, they have n'ientionedamines under the reaction conditions not met with unqualified success. For example, employed. mav be uti1ized.- Examples of such when employing such silvering compositions it sil er compounds are the nitrate. sul ate,acetate.

was necessary to always use a freshly-prepared chlorateoxide; cyanide. fluoride. chloride, and

ammoniacal silver solution since if such solus l' r p tassium cyanide. tions .were permitted toYstand for any period 7 The base utilized in preparing silver ing comof time silver fulmi-nate, a highly explosive map i ons o the time contemplated bv the presterial, was formed. Furthermore, it was gen 40 en inven i n may be any o a number of ma erally necessary to carry out the silvering proc- W118 having an al ne reaction. As ex p ess at relatively low temperatures in order to o uch compounds there may be mentioned the prevent the formation of such explosive suba e sol ble hvdroxides, carbonates. and bicarstances. Also, the alkalinity of these oomposi -z b ner-es of the alkali and alkaline earth metals. tions was a factor to be closely controlled inas- 5 Al o. ammon a and the alkyl -substituted ammuch as excessive quantities of alkali resulted m ies. or amines. such as. 2-amin'obutane. triin the deposition of dark and irregular silver methvlamin diethylamine. N-(2-aminoi5nfilms. r butyliisopropylamine. etc. may be emploved i I have now discovered certain novel coml eu of bas c materials of'the above-mentioned positions and a method fo pp y ng the same, '50 tvpe. and it is to be specifically understood that the term base. used in certain of the claim i cludes such compounds. When employin al- 'kaline' substances of the latter class I have found that the time required for deposition of the silver is somewhat longer than that necessary when using stronger bases, such as for example,

tion had-been added.

sodium hydroxide. However, the mirrors produced when utilizing ammonia or the various alkyl-substituted ammoniasvare quite satisfactory. It should also be noted that when empioyingthe latter type of alkaline agents, mirrored surfaces possessing good-reflecting properties may be obtained by omitting the use of any additional base other than that required.

to form the silver ammonia complex. The nitro alcohols used are broadly deflned'by the above generic structural formula, specific ex- 1 amples of such compounds being tris hydroxymethyl) nitromethane, 1,1-bis (hydroxymethyl) 1- nitro-2-propanol, z-ni'tro-Lii-propanediol, -2- nitro-Z-methyl-1,3!propanediol, 2-nitro-2-ethylwas added thereto, with agitation.

2-ethyl-1,3-propanediol was prepared, after which 40 parts of 0.5 molar aqueous barium hydroxide During the additionof the barium hydroxide,which was carried out at room temperature, deposition of silver on the walls of the containing vessel was observed.

I The mirror thus formed reached its maximum 1,3-propanediol, Z-nitro-Z-methyl-l propanol, 2-',

nitro-l-propanol, 2-nitro-l-butanol, 2- nitro-3- pentanol, 3-nitro-3-methyl-2-butanol, 2-nitro-4- ethyl-3-pentanol, 2-nitroe2-ethyl-3-hexanol, 3-

3-nitro-4-decanol, and the like. In connection withthe use of the above nitro alcohols, it is frequentl'y desirable tov employ a'small quantityof a lower aliphatic jalcohol, such as ethyl alcohol, in

order to obtain a homogeneous silvering solution.

This has been found torbe particularly true ,with nitro alcohols of increasing molecular weight.

In carrying out" my invention in accordance with the above general description, it will readily occur to those skilledin the art that" a mixture 'of suitable silver salts, as well as amixture of nitro alcohols and/or bases, may be utilized; In any event, it can readily be determined by way of "simple experiment what silver salt and nitro alcohol or combinations thereof should be used in upon the surface, with which the solution is in contact, to give an even and unpitted reflecting surface. a The examples which follow are'typical of'both the compositions and procedure employed in carrying out my invention.

Example I 7 1 Into a suitable vessel was introduced 40 par of 0.4 molar aqueous silver nitrate solution; ap-' proximately 20 parts of molar aqueous ammania, and 0.4 part of tris(hydroxymethyl)nitro-' methane. To this resulting aqueous mixture, which consisted principally. of diammine-silver nitrate [Ag(NH3)2NO3] and tris(hydroxyine tl4!l) 'nitromethane was then added at a temperature -nitro-4-heptanol, 2-nitro-1-phenyl-l-propanol,

' order to eflect a satisfactory deposition of silver the .vessel walls.

was thoroughly agitated and maintained at a 1 temperature of about 29 C. Approximately 15 minutes after-all of the Z-aminobutane had been introduced, a bright silver mirror appeared on V I p Erdmple V Abright silvered reflecting surface was prepared in the same manner as described in Example IV by'employing2.4 parts of diethylamine instead of the Z-aminobutane specified in Example IV.. v V V V Example VI To 40 parts of 0.4 molar aqueous silver nitrate was added 10 parts of 4' molar aqueous ammonia.

,This' mixture was then heated to a temperature of C.,' after which was added thereto 10 parts of 0.4 molar aqueous 2-nitro-2-ethyl-1,3-pro-' panediol. A brilliant mirror was formed on the vessel walls within a few minutes after the addition of the latter compound.

' The silvered reflecting suri aces obtained in accordance with the procedures outlined above may be finished by washing with'water and then covered with a suitable coating material, such as clear varnish, shellac, or clear lacquer. Reflecting surfaces of the type described above may be satisfactorily produced upon such materials as glass, copper, nickel, and zinc. Alterations in procedure required'to produce satisfactory reflectingfsurfa'ces on such materials will be apparent tothose familiarwiththe art. Also other modifications in 'the reaction conditions and compositions; employed will be obvious, and it is intended that such alterations and modifications shallbe interpreted as lying within the scope of of about 30 C., with continuous'stirring, 10 parts 'of 2 molar aqueous sodium hydroxide. Durin the addition'of the a'queoussodium hydroxide so-j lution, a bright silver mirror surface was formed upon the walls of the've'ssel, the, mirror attaining,

its maximum' degree of brilliancy shortly: after the entire quantity of the sodium hydroxide solu- Example II in the same manner as described in Example'I,

' A bright silvered reflecting surface was prepared by employing a solution .consistingof 1.3 parts of 3-nitro-4-heptanol', 30 parts'of ethyl-alcohol and 10 parts of 4 molar aqueous ammonia, in place 7 V 1 Example III A homogeneous solution-containing 40parts of 0.4 molar aqueous silver nitrate, 10 parts of, 4 .molar aqueous ammonia and 1.2 parts of 2-nitrooffthe tris(hydroxymethyl)nitromethane and 15 molar aqueous ammonia specified inExample I. so

my invention.

1 My invention now having been described, what 'I claim is: 1. Acomposition capable of producing reflect ing surfaces, comprising a silver ammonia complex, a base, and'a nitrohydroxy compound having thejstructural formula:

j 4 No. 0H

wherein R and RF represent a member selected from the group consisting of hydrogen, hydroxyalkyl, and alkyl, and R represents a member selected from the group consisting of hydrogen, aryl, and alkyl,

2. A composition'capable of producing a reilecting surface, containing essentially and in reactive proportions, diammine-silver nitrate, so-

dium' hydroxide, and 3nitro-4-heptanol.

3. A composition capable of producing a reflecting surface, containing essentially and in reactive proportions, diammine-silver nitrate, 2- aminobutane, and 2-nitro-2-ethyl-1,3-propanediol.

4. A composition capable of producing a re-' fleeting surface, containing essentially and in reactive proportions, diammine-silver nitrate, sodium hydroxide, and tris(hydroxymethyl)nitromethane.

5. A method for producing a silvered reflectin surface, comprising reacting a silver ammonia complex, in the presence of a base, with a nitrohydroxy compound of the formula:

wherein R and R represent a member selected from the group consisting of hydrogen, hydroxyalkyl, and alkyl, and R represents a member selected from the group consisting of hydrogen,

surface comprising reacting a silver ammonia complex with his (hydroxymethyl)nitromethane in the presence of sodium hydroxide, said reaction being effected in the presence of the surface to be silvered.

8. A method for producing a silvered reflecting surface comprising reacting a silver ammonia complex with W-nitro-2-ethyl-1,3-propanediol in the presence of 2-amin'obutane, said reaction being effected in the presence of the surface to be silvered.

PHILIP 'F. TRY'oN. 

